findwindow 后postmessage点解按钮

HWND    hWnd1,hWnd2;  

        hWnd1 = ::FindWindow(NULL,_T("Dlg"));
        if(hWnd1)  
        {

                hWnd2 = ::FindWindowEx(hWnd1,NULL,_T("Button"),"&Yes");
                if(!hWnd2) 
                hWnd2 = ::FindWindowEx(hWnd1,NULL,_T("Button"),"是(&Y)");


            if(hWnd2)
            {  
                ::PostMessage(hWnd2,WM_LBUTTONDOWN,MK_LBUTTON,MAKELPARAM(0,0));
                ::PostMessage(hWnd2,WM_LBUTTONUP,MK_LBUTTON,MAKELPARAM(0,0));  

                 ::PostMessage(hWnd2,WM_LBUTTONDOWN,MK_LBUTTON,MAKELPARAM(0,0));        
                 ::PostMessage(hWnd2,WM_LBUTTONUP,MK_LBUTTON,MAKELPARAM(0,0));
            }
        }